GB2140624A

GB2140624A - Push-button switch

Info

Publication number: GB2140624A
Application number: GB08413375A
Authority: GB
Inventors: Yasuo Matsui
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1983-05-24
Filing date: 1984-05-24
Publication date: 1984-11-28
Also published as: DE3419426A1; KR890001961Y1; KR840006410U; JPS59182827U; GB8413375D0

Abstract

A push-button switch having a casing (1) provided with a recess (2) in which fixed and movable contacts (5, 6) are mounted. A stem (7) for deforming the movable contact (6) into and out of contact with the fixed contacts (5) is covered by an elastomeric cover (11) having a flange (12) held to the fringe of the opening to the recess. This opening has a step (17) on which the flange (12) is placed. A pad (16) made from welded metal is formed around the opening and bent over to hold the flange (12) between the pad (16) and the upper surface of the step (17). <IMAGE>

Description

SPECIFICATION Push-button Switch Field of the Invention The present invention relates to an improved push-button switch.

Background of the Invention A push-button switch having fixed contacts, and a movable stem engaging a movable contact has heretofore been known. The stem can be reciprocated by actuation of a push button to move the movable contact into and out of contact with the fixed contacts.

Such a push-button switch is often installed to a printed circuit board by soldering or the like, and a flux is thus often used. At this time, there arises a possibility that the flux, dust or the like may intrude into the recess of the switch of the conventional structure, resulting in inferior contact between the contacts. Further, the casing is often cleaned with a solvent to remove foreign matter such as flux that may become attached to the outer wall of the casing during the manufacturing process of the switch, and great care must be taken to prevent solvent from entering the casing of the switch. Hence, a quite cumbersome operation is required.

Summary of the Invention The present invention has been devised in view of the foregoing problems with the prior art device. It is the main object of the present invention to provide a push-button switch which can prevent foreign matter such as flux from intruding into the switch and which facilitates removal of foreign matter clinging to the casing.

The push-button switch according to the present invention is characterized in that an elastomeric cover having a flange closes the recess and covers the stem, and the fringe of the opening to the recess is provided with a step so that a deformable pad may be bent over to hold the flange between the pad and the upper surface of the step.

Brief Description of the Drawings Fig. 1 is a longitudinal cross section of a pushbutton switch according to the present invention; and Fig. 2 is an exploded perspective view of the push-button switch shown in Fig. 1.

Detailed Description of the Invention Referring to Figs. 1 and 2, there is shown a push-button switch embodying the concepts of the present invention. The switch includes a casing 1 that is provided with a recess 2 having an open 3. Fixed terminals 4 are attached to the lower portion of the casing 1. Fixed contacts 5 and a movable contact 6 are mounted to the bottom of the case 2. The movable contact 6 takes the form of a curved disk and can be resiliently deformed. A stem 7 which has disklike portion 8 and a cylindrical protrusion 9 can reciprocate within the recess 2. The bottom of the disklike portion 8 is provided with a semicircular projection 10 adapted to engage the movable contact 6. The stem 7 acts to deform the movable contact 6 to bring it into or out of contact with the fixed contacts 5.An elastomeric cover 11 is fitted over the cylindrical protrusion 9 of the stem 7, and is made from a rubber-like material such as chloroprene rubber having a small degree of swelling when brought into contact with conventional solvents. The cover 11 has a flange 12 and a recess 1 3 in which the cylindrical protrusion 9 of the stem 7 is fitted. The stem 7 is covered by the cover 11.

The opening in the upper surface of the casing is provided with a step 1 7 on which the flange 12 of the cover is placed. A pad 1 6 formed from welded metal is placed around the opening on the upper surface of the casing 1. The upper portions of the pad 1 6 can be staked or bent inwardly to hold the flange 12 between the pad and the upper surface of the step 17. Further, the upper surface of the step 17 is provided with an annular protrusion 1 5 which presses into the pad 1 6 to increase the clamping of the flange 12 and hold the pad 1 2 in position. The rubber cover 11 is held to the casing 1 so as to close the recess 2, and has an annular recess 18 between the recess 13 and the flange 12.The recess 18 receives the fringe portion 1 9 of the pad 1 6. The fringe portion 19 is curved downwards toward the annular protrusion 15, and cooperates with the annular protrusion 14 to tightly clamp the flange 12. The flange 1 2 is held against the support wall 14 along its whole peripheral length. The pad 1 6 is bent by means of a spinning staking means or thermal staking means.

In this embodiment, the rubber cover 11 is made from a material having a small degree of swelling and is provided with the flange 12 which is clamped in the direction of its thickness in such a manner that the recess 2 is closed. Accordingly, foreign matter such as flux will not be able to enter the recess 2 so that the switch can maintain its switching performance. When the casing 1 is cleaned to remove the foreign matter such as flux clinging to the casing 1 by immersing the switch entirely in a solvent such as Freon, the solvent cannot enter the recess 2. Further, the cover 11 does not swell nor from the solvent deform, permitting the switch to be cleaned as a unit without impairing the function of the cover 11.

Consequently, a plurality of such switches can be cleaned at a time in an efficient way.

As thus far described, in the novel push-button switch, the stem is covered by an elastomeric cover provided with a flange to close the recess containing the stem. Therefore, the novel switch can have the advantage that it can prevent flux or dust from entering its recess when a soldering operation is effected, thereby preventing deterioration in the switching performance. In addition, the switch can be immersed in a solvent without the solvent intruding into the recess. Hence, a plurality of such switches can be cleaned at a time in an efficient manner.

While a preferred embodiment has been described, variations thereto will occur to those skiiled in the art within the scope of the present invention concepts which are delineated by the following claims.

Claims

1. A push-button switch comprising: a casing having a recess containing fixed contacts and a movable contact; means including a stem extending into said recess through an opening in said casing for bringing said movable contact into and out of contact with said fixed contacts; an elastomeric cover having a flange held to said opening and a portion fitting over the stem in such a way that the opening to said recess is closed, said opening being provided with a step on which said flange is placed; and a deformable pad extending around said opening and adapted to be bent over to hold said flange between said pad and the upper surface of said step, said pad being formed of metal welded around said opening.

2. A push-button switch as set forth in claim 1, wherein the elastomeric cover is made from a material that swells by a small factor when immersed in solvent.

3. A push-button switch as set forth in claim 1, wherein the elastomeric cover is made from chloroprene rubber.

4. A push-button switch substantially as hereinbefore described with reference to the accompanying drawings.